JPS6250402B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a new method for producing fine metal carbides via a new carbon-containing mixture. [Background Art] Metal carbides have conventionally been produced by reacting mixtures of metal oxides and carbon under ignited heat. For example, silicon, titanium, tungsten, boron, aluminum, zirconium, hafnium,
It is carried out industrially by mixing single metals such as niobium, cobalt, molybdenum, tantalum, chromium, vanadium, or one or more of these metal oxides with carbon and reacting the mixture under ignited heat. That is, when these single metals or mixtures of these metal oxides and carbon are heated as they are or in an inert gas such as argon or helium in a high-frequency heating furnace, an Acheson type direct current resistance furnace, etc., a reduction reaction occurs. A carbonization reaction occurs,
SiC, TiC, WC, B ₄ C, ZrC, HfC, NbC,
Metal carbide powders such as Mo ₂ C, TaC, Cr ₃ C ₂ , VC, etc. are manufactured. Also, by heating a mixture of two or more single metals or metal oxides and carbon, (SiTi)C, (WTi)C, (MoW)C,
Composite metal carbide powders such as (WTiTaNb)C have been produced. The finer the metal carbide powder, the stronger the molded product obtained by sintering and processing it, and the faster the sintering speed. Therefore, it is required that fine particles are uniformly mixed in the intermediate raw material, which is a mixture of a single metal or an oxide of these metals and carbon. In conventional technology, in order to satisfy this requirement of a mixture as uniform and fine as possible, coarse grained or lumpy single metals or metal oxides and carbon are usually mechanically pulverized and mixed using a ball mill, hammer mill, etc. It is common to perform both at the same time in a batch method. However, since the mechanical method using ball mills etc. is a batch method, the work process is complicated when mixing and charging raw materials, and when unloading, and a large amount of dust is generated, and noise is generated during pulverization and mixing. There are problems with the work environment. In addition, mechanical pulverization requires pulverization for a long time, for example, one week, which inevitably increases the amount of impurities mixed in due to wear of the pulverizer itself. Due to this problem, impurity removal processes such as chemical cleaning and adsorption are required as post-processes. Because of these problems, it is essentially impossible in principle to obtain an ultrafine mixture of 1 micron or less using such a mechanical method. On the other hand, a method is also known in which already fine powder obtained by some method is mixed. For example, there is a method of mixing each fine powder using a mixer, kneader, etc., but this method has the problem of generating a large amount of dust, as well as the differences in particle size, orientation, and specific gravity inherent to the powder. The unavoidable disadvantage is that the mixture content is uneven. Therefore, as a further improved method,
As described in Publication No. 50-127900, two or more types of fine powder are colloidally dispersed in water etc.
There is a method of spray drying using a spray dryer, or as described in Japanese Patent Publication No. 51-13262, two types of carrier gas each containing fine powder are combined and the two are mixed in the gas phase. A method has also been proposed in which the two types of powder are mixed in the gas phase. However, even with this method, it is unavoidable that the mixture contents will vary from a microscopic perspective, and an even more fundamental problem is that silicon oxide powder and titanium oxide powder ,
Powders such as carbon powder particles are usually easily separated by 50% each.
Approximately 100 particles are tightly bound together to form so-called secondary aggregates, and these aggregates cannot be easily separated into single particles. Even if you try spray drying or gas phase mixing, it is impossible for these to be completely separated and they will simply remain in the same form as aggregates. There is a fundamental and fundamental problem in that it is difficult for each substance to form a mixture that exists independently. On the other hand, as a known technique for obtaining metal carbides, metal halides such as boron, silicon, titanium, zirconium, hafnium, vanadium, tantalum, niobium, molybdenum, tungsten, thorium, etc., and hydrocarbons and hydrogen are directly finalized by gas phase reaction. A method for producing the target fine metal carbide in one step has been proposed in US Pat. No. 3,839,542. However, this direct method (one-stage method) requires the use of plasma as a heating method and the need to supply a large amount of hydrogen gas.
It has the disadvantage that it requires a temperature higher than ℃. In addition, as another direct method, metal halides selected from Groups 3 to 5 of the Periodic Table of Elements, carbon sources, nitrogen sources, etc., and anhydrous hydrogen halides are directly reacted in the gas phase to form metal carbides. A method for manufacturing is known as Japanese Patent Publication No. 56-36122. However, this method also has major drawbacks in that it requires the supply of a large amount of hydrogen gas and also that it requires the supply of anhydrous hydrogen halide. In addition, in these conventional methods of directly producing the final target metal carbide in one step by gas phase reaction, the presence of oxygen and hydrogen gas greatly inhibits the production of the target metal carbide. In addition, it is difficult to carry out the reaction in one step, and even if the reaction is carried out at a high temperature, the yield is extremely low and a considerable amount of the raw material metal halide remains unused. There is a fundamental problem in that it escapes out of the reaction system in the gaseous state of the reaction. [Object of the Invention] The object of the present invention is to provide a method that can be obtained without performing mechanical grinding and mixing operations such as ball mills and hammer mills, which have many problems such as noise, abrasion, contamination of impurities, and generation of dust. To provide a new method for producing extremely fine metal carbide using a new carbon-containing mixture (mixed powder) made of extremely uniform mixture of fine particles of carbon and a desired metal oxide as a raw material. be. [Disclosure of the Invention] As a result of thorough consideration of the advantages and disadvantages of these conventional techniques, the present inventors have found that in order to obtain a metal carbide with excellent physical properties, it is not necessary to directly obtain the desired product from raw materials, but to obtain a sufficiently homogeneous metal carbide. We have discovered that by obtaining a mixture (mixed powder) of carbon and metal oxides with high properties and fine constituent particles and then heat-treating this, it is possible to obtain a target product of excellent quality very easily. The invention has been completed. That is, the above object of the present invention is to charge and decompose a decomposable metal compound and a decomposable carbon compound into a hot gas containing water vapor to produce a mixed aerosol dispersion containing aerosols of metal oxides and elemental carbon, respectively. This is achieved by a novel method for producing metal carbides, which is characterized by generating a carbon-containing mixture, collecting the generated dispersoids, and heating the resulting carbon-containing mixture. The present invention will be explained in detail below. The novel "carbon-containing mixture" in the present invention is
It is characterized by being obtained by charging a decomposable metal compound and a decomposable carbon compound into a water vapor-containing gas to generate a mixed aerosol of metal oxide and carbon, and collecting this dispersoid. It refers to a product in which fine particles of elemental carbon and metal oxide are uniformly mixed on a microscopic scale, and it appears to be a "mixed powder." In addition, the term "mixture" here refers to "a mixture of two or more substances that exist homogeneously as a whole and are understood as a single substance", so it is exactly the same as the "mixture" mentioned in the industrial examination standards. Although it should originally be called a "carbon-containing composition," the term "carbon-containing mixture" was used here for the sake of custom. The mixed aerosol referred to in the present invention refers to a gas in which carbon and metallic solid dispersoids are mixed, and because the solid dispersoids are fine, they have fluidity and It is a mixture in which each powder exhibits a uniform dispersion system with high mobility in the gas. According to the findings of the present inventors, it is an object of the present invention that the nitrogen adsorption specific surface area of the powdered solid of the mixture in which the dispersoids are collected is at least 3 m ² /g or more, preferably 30 m ² /g or more. preferred. Nitrogen adsorption specific surface area (so-called BET)
(value determined by method) is used as a simple measure to indicate the average particle diameter of powdered solids, but since each powdered solid has its own unique shape and particle size distribution, for the entire powder, It is extremely difficult to accurately measure and display particle size and particle size distribution.
For this reason, it is convenient to measure the amount of nitrogen gas adsorbed on the surface of a solid material and use this as a measure corresponding to the average particle diameter. A large nitrogen adsorption specific surface area means a small average particle diameter. In addition, as a result of directly observing the shape of the particles constituting the carbon-containing mixture using an electron microscope, it was found that when the nitrogen adsorption specific surface area of the carbon-containing mixture is 3 m ² /g or more, the average particle diameter of the carbon-containing mixture is approximately 1 μ or less. The inventors of the present invention have experimentally confirmed that the thickness is approximately 0.1 μ or less when the surface area is 30 m ² /g or more. Here, regarding the electron microscopic images of particles etc. of carbon-containing mixtures, the original application of this application, which is a divisional application, was filed in Japanese Patent Application No. 57
- As shown in the attached drawings 2 to 6 of No. 158786. The metals constituting the decomposable metal compound in the present invention include lithium, sodium, potassium,
Group A metals such as rubidium and cesium; Group A metals such as beryllium, magnesium, calcium, strontium, and barium; Group A metals such as titanium, zirconium, and hafnium; Group A metals such as vanadium, niobium, and tantalum; chromium, molybdenum; Group A metals such as tungsten, Group A metals such as manganese, technetium, and rhenium; Iron group metals such as iron, ruthenium, and osmium; Cobalt group metals such as cobalt, rhodium, and iridium; Nickel group metals such as nickel and palladium; copper , Group B metals such as silver and gold, Group B metals such as zinc, cadmium, and mercury, Group B metals such as boron, aluminum, gallium, and indium, Group B metals such as silicon, germanium, tin, and lead, phosphorus, and arsenic. , B group metals such as antimony and bismuth, B group metals such as sulfur, selenium, tellurium, cerium, praseodymium,
These include rare earth metals such as neodymium, thorium, and uranium, and among the halides, alkylated products, alkoxide compounds, and acid esterified products of these metals, they are easily thermally decomposed, oxidized, or hydrolyzed in hot gas containing water vapor. and gives an oxide of the metal. Examples of such decomposable metal compounds include C ₅ H ₁₁ Li, C ₃ H ₅ Li,
C ₅ H ₅ Li, LiH, NaH, C ₅ H ₅ Na, C ₆ H ₅ C ₂ Rb,
C ₆ H ₅ CH ₂ Rb, C ₂ H ₅ Cs, C ₆ H ₅ C ₂ Cs,
_{( C2H5} ) _2Be , ( _CH3 ) _2Be , _{C3H5MgCl ,}
( _CH3 ) _2Mg , Mg( _OCH3 ) ₂ , _C2H5Na , _Mg
(OC ₂ H ₅ ) ₂ , (C ₅ H ₅ ) ₂ Ca, CaH ₂ , Sc(CH ₃ ) ₃ , Y
( _CH3 ) ₃ , Y _{( C5H5} ) ₃ , La( _CH3 ) ₃ , La
( _CH3 ) ₃ , La _{( C5H5} ) ₃ , _TiCl4 , _{TiCl3CH3 , TiCl3
( C5H5} ), _{TiF4 , TiBr4} , _TiI4 , Ti( _C5H5 ) ₂ , Ti
( _{OC3H7 ) 4} , _ZrCl4 , _ZrBr4 , _ZrI4 , _ZrH2
( _C5H5 ) _{2 ,} Zr( _{OC2H5 ) 4} , Zr( _OC3H7 ) ₄ , _{HfCl4 ,
Hf} ( _C3H5 ) ₄ , _{HfCl2 ( C5H5} ) ₂ , Hf _{( OC4H9} ) ₄ ,
VF ₅ , VCl ₄ , V(C ₅ H ₅ ) ₂ , V(C ₆ H ₆ ) ₂ , NbF ₅ ,
NbCl ₄ , NbCl ₅ , NbBr ₅ , Nb(C ₃ H ₅ ) ₄ , Nb
( _OC6H5 ) _{5 , TaF5} , _TaCl4 , _TaCl5 , _TaBr4 ,
_TaCl2 ( _CH3 ) ₃ , _TaH3 ( _C5H5 ) ₂ , _Ta
( _OC2H5 ) _{5 , CrCl4} , _{CrO2Cl2 ,} Cr( _CH3 ) ₄ , _Cr2
( _C3H5 ) ₄ , _MOF5 , _MOF6 , _MOCl5 , _{MOCl4O ,}
MOCl ₂ (C ₅ H ₅ ) ₂ , MOH ₂ (C ₅ H ₅ ) ₂ , WF ₆ ,
WCl ₄ , WCl ₅ , WCl ₆ , W(CH ₃ ) ₆ , WH ₂
(C ₅ H ₅ ) ₂ , WCl ₂ (C ₅ H ₅ ) ₂ , W(OC ₆ H ₅ ) ₆ , Mn
( _{C5H5 ) 2} , TCH( _C5H5 ) ₂ , ReH( _{C5H5 ) 2} , _FeCO
(C ₄ H ₆ ) ₂ , Ru (C ₅ H ₅ ) ₂ , Co (C ₅ H ₅ ) (C ₆ H ₈ ), Co
(CO) ₂ C ₅ H ₅ , Co (C ₃ H ₅ ) ₃ , Rh (C ₅ H ₅ )
((C ₅ H ₆ ), Ni(C ₃ H ₅ ) ₂ , [IrCl(C ₈ H ₁₄ ) ₂ ] ₂ , Ni
( _{C5H5 ) 2} , Pb( _C3H5 )( _C5H5 ) _{, ZnH2} , _Zn
( _C2H5 ) ₂ , Cd( _CH3 ) ₂ , Cd( _{C2H3 ) 2} , _HgF2 , _Hg
( _CH3 ) ₂ , _BF3 , _BCl3 , _BBr3 , B( _OCH3 ) ₃ , B
(OCH ₃ ) ₂ (OH), B(OC ₂ H ₅ ) ₃ , B(OC ₆ H ₅ ) ₃ ,
_{B2H6 ,} B( _CH3 ) ₃ , _AlH3 , _{AlCl3 ,} ( _C2H5 ) _3Al ,
Al( _OCH3 ) ₃ , Al( _OC2H5 ) ₃ , Al _{( OC3H7} ) _{3 ,}
GaCl ₃ , GaBr ₃ , Ga(CH ₃ ) ₃ , Ga(C ₆ H ₅ ) ₃ ,
( _C2H5 ) _2GaOC2H5 , _{InCl2 , TlF3} , _Tl ( _{CH3 ) 3} ,
SiH ₄ , Si ₂ H ₆ , SiCl ₄ , SiF ₄ , Si(OC ₂ H ₅ ) ₄ ,
( _CH3 ) _{2SiCl2 , CH3SiCl3 ,} ( _CH3 ) _4Si ,
( _C2H5 ) _4Si , _{HSiCl3 , H2SiCl2 , GeCl4} ,
( _CH3 ) _4Ge , Sn( _CH3 ) ₄ , _PbF4 , _PbCl4 ,
( _C4H9 ) _4Pb , _PH3 , _PCl4 , _AsF3 , _AsF5 , _{AsCl3 ,}
SbCl ₅ , BiH ₃ , BiF ₅ , BiCl ₃ , Ce(C ₅ H ₅ ) ₃ , Th
(C ₄ H ₉ ) ₄ , UF ₆ , U (OCH ₃ ) ₅ , U (OCH ₃ ) ₆ , U
Preferred examples include compounds such as (OC ₃ H ₇ ) ₅ , but as mentioned above, the compound is not limited thereto as long as it is decomposable in hot gas containing water vapor. These may be used alone or in combination of two or more. These decomposable metal compounds are charged into a hot gas containing water vapor. Some of these compounds are solid at room temperature, but even these compounds can be easily charged into the reaction zone by being heated to a temperature necessary for melting beforehand. The decomposable carbon compound used in the implementation of the present invention is
When charged in a hot gas as described later, it can easily decompose and produce elemental carbon (soot), and it is either in the gas phase or liquid phase as it is, or
Those that can be easily turned into a liquid phase by increasing the temperature can be suitably used. Petroleum products such as LPG, naphtha, gasoline, fuel oil, kerosene, light oil, heavy oil, lubricating oil, liquid paraffin; methane, ethane, propane, butane, pentane, methanol, ethanol, propanol, ethylene, acetylene, n
- Paraffin, butadiene, isoprene, isobutylene, benzene, toluene, xylene, cyclohexane, cyclohexene, dicyclopentadiene, ethylbenzene, styrene, kyumene, pseudocumene, mesitylene, alkylbenzene, α
-Methylstyrene, dicyclododecatriene, diisobutylene, vinyl chloride, chlorobenzene,
Petrochemical products such as _C9 distillate mixtures and ethylene bottoms; tar products such as tar, pitch, creosote oil, naphthalene, anthracene, carbazole, tar acid, phenol, cresol, xylenol, pyridine, picoline, and quinoline; large Preferred examples include, but are not limited to, oils and fats such as bean oil, coconut oil, linseed oil, cottonseed oil, rapeseed oil, tung oil, castor oil, whale oil, beef tallow, squalane, oleic acid, and stearic acid. . The decomposable carbon compound used in the practice of the present invention is
Since the purpose is to supply carbon, a wide range of choices can be made from this purpose, for example as described above. However, from the viewpoint of ease of handling and carbon yield, toluene, xylene, benzene, kerosene, light oil, heavy oil, _C9 distillate mixture, ethylene bottom, etc., which have a relatively large carbon content, are particularly preferred. The above-mentioned metal compounds and carbon compounds used in the present invention are usually already in the state as they are, or can be easily converted into a gas or liquid phase, and when it is necessary to remove specific impurities, distillation, adsorption, or
Since this can be achieved by simple operations such as washing, a highly pure mixture can be easily obtained. Further, the ratio of metal to carbon in the carbon-containing mixture of the present invention can be adjusted simply by adjusting the amount of injection from the nozzle. The metal compounds that can be used in the practice of this invention can be selected from a wide range as described above. However, in particular, we manufacture raw material powder for sintered bodies of carbides of metals such as silicon, titanium, tungsten, boron, aluminum, zirconium, hafnium, niobium, molybdenum, tantalum, chromium, and vanadium, which are heat-resistant and corrosion-resistant ceramic materials. In order to obtain the _carbon -containing mixture of the present invention containing metal oxide and carbon as corresponding intermediate raw materials,
_SiF4 , _CH3SiCl , ( _CH3 ) _{2SiCl2 , TiCl4} , _TiF4 ,
WCl ₂ , WCl ₅ , WCl ₆ , BF ₃ , BCl ₃ , B
( _OCH3 ) ₃ , _B2H6 , _{AlCl3 ,} Al( _OCH3 ) ₃ , Al
( _OC2H5 ) ₃ , Al _{( OC3H7} ) _{3 , ZrCl4} , _ZrCl2O ,
_ZrBr4 , Zr _{( OC3H7} ) ₄ , _HfCl4 , _NbCl4 , _MoCl5 ,
_{TaCl4 ,} Ta( _OC2H5 ) ₅ , _CrCl4 , _{CrO2Cl2 , VCl4}
Decomposable metal compounds such as the following can be suitably used. In addition, metals suitable as sintering aids and physical property improvement aids are added to the intermediate raw materials in advance by sintering the metal carbide obtained by heat treating the carbon-containing mixture, which is the intermediate raw material, and producing molded bodies. It is also suitable for the purpose of the present invention to add it at the stage of producing the carbon-containing mixture of the present invention. Metal compounds suitable for such auxiliaries include C ₂ H ₅ Cs, BeCl ₂ , Y(CH ₃ ) ₃ , Ni(CO) ₄ ,
_ZnH2 , _PCl3 , _BiCl3 , Mg( _OCH3 ) ₂ , Mg
There are decomposable metal compounds such as (OC ₂ H ₅ ) ₂ and COCl ₂ . A furnace is used in the practice of the invention. The heating device is preferably a device that includes a combustion burner, an energized heating element, etc., and is equipped with a nozzle for charging the metal compound or carbon compound, a hot gas charging duct, and a mixed aerosol discharge duct, and is surrounded by a refractory material. used for. In the present invention, there must be a spatial region in the furnace at least 600°C or higher, preferably 700°C or higher, more preferably 800°C or higher. At temperatures above this temperature, metal oxides are obtained as aerosols from metal compounds mainly through hydrolysis reaction with water vapor, and further through thermal decomposition and oxidation, and elemental carbon is obtained from carbon compounds as aerosols. Generates a mixed aerosol state that is a mixture.
Note that a temperature of 2000°C or higher is usually unnecessary as it only causes heat loss. Further, even if a metal element, a metal hydroxide, or even a metal halide is interposed in addition to the metal oxide, this does not interfere with obtaining the metal carbide that is the final objective of the present invention. Hot gas containing water vapor can also be obtained by injecting water vapor into hot gas obtained by an electric heating method, a high frequency heating method, or a discharge method. This method uses air to combust combustible materials that produce water vapor when burned, such as ethane, propane, or hydrocarbons used as raw materials. Because hot gas containing water vapor can be obtained in one step, the equipment is simple and thermally efficient. It is economical in terms of As mentioned above, the decomposable metal compound used in the practice of the present invention is easily converted into a solid metal by a thermal decomposition reaction in hot gas, and also undergoes metal oxidation by a hydrolysis reaction with water vapor. The reaction rate is extremely high (the reaction is substantially completed in about 0.01 to 0.1 seconds, so the reaction time (residence time in the reaction zone) is 1. (Seconds are enough)
Therefore, in an atmosphere where heat and water vapor coexist as in the present invention, it is virtually negligible that the metal compound evaporates out of the reaction system while remaining in a gaseous state. The mixed aerosol dispersoid in the hot gas thus obtained is guided outside the furnace, and the solid matter contained therein is captured by a solid-gas separation operation using a known collection device such as a bag filter, cyclone, or electrostatic precipitator. However, in order to reduce the heat load on the collection device, it is desirable to cool it beforehand. As a method of cooling, the zone after the reaction may be cooled, or water may be injected. The collected carbon-containing mixture of the present invention can be turned into the metal carbide powder or composite metal carbide powder of the present invention by heating it. The heating temperature can be appropriately selected depending on the type of metal carbide of interest, but is approximately 1000 to 2500.
The temperature preferably ranges from about 1200 to 2000°C. It is advantageous to use a non-oxidizing atmosphere such as argon, hydrogen, or nitrogen depending on the conditions as the heating atmosphere to prevent elemental carbon from being dissipated by combustion. However, in the present invention, if a metal carbide is generated by heating the carbon-containing mixture, carbon monoxide is simultaneously generated and the system naturally becomes a non-oxidizing atmosphere. Therefore, in the present invention, a non-oxidizing gas is particularly introduced. There's no need. To give a more specific example, the carbon-containing mixture of the present invention is ignited and subjected to a reduction reaction and a carbonization reaction to produce SiC, TiC, WC, B ₄ C, ZrC, HfC,
Metal carbides such as NbC, Mo ₂ C, TaC, Cr ₃ C ₂ and VC can be easily obtained. [Operations and Effects of the Invention] As described above, in the present invention, a decomposable metal compound and a decomposable carbon compound are subjected to a chemical reaction, that is, thermal decomposition, oxidation, hydrolysis, etc., in a hot gas containing water vapor. The properties of the particle mixture are significantly superior to those produced by conventional mechanical mixing methods. In addition, there are no problems such as dust or noise in its implementation, and unlike the batch method, the mixture can be obtained continuously, which significantly reduces the complexity of the conventional work process. There are no problems with contamination. or,
Compared to wet mixing and spray drying methods, this method is much simpler and has the advantage that a uniform and fine mixture can be easily obtained. Furthermore, when the present invention is carried out, metal carbide is obtained through a mixture consisting of extremely uniform and fine aerosol dispersoids as described above, so the metal carbide powder obtained has an extremely large specific surface area, and also has a very large specific surface area. Since the metal carbide particles produced are extremely small, the sintering speed is fast, sintering is easy, and a dense product can be obtained. Furthermore, if the ratio of carbon to metal in the carbon-containing mixture is made excessive, the resulting metal carbide powder can be easily obtained, which is fine and has a large specific surface area. The amount of carbon in the carbon-containing mixture of metal oxide and elemental carbon in the present invention is of course not a critical requirement and can be freely changed depending on the purpose. That is, for example, in order to obtain a minute metal carbide, the formula ratio of carbon to metal (g-atom carbon/g-atom metal; hereinafter the same) is determined by the stoichiometric amount of carbon required to form the metal carbide. It is preferable that the ratio is higher than the theoretical ratio. For example, to give a specific example, when the metal is Si or Ti and you want to obtain its carbide SiC or TiC, the reaction formula is naturally SiO ₂ +3C→SiC
+2CO, or TiO ₂ +3C→TiC+2CO, so it can be seen that the formula ratio of carbon to metal must be at least 3 or more. In the case of B, the reaction formula is 2B ₂ O ₃ +7C→B ₄ C+6CO, so the formula weight ratio is at least 7/4. It goes without saying that excess carbon can be easily removed from the metal carbide obtained here by heating it to 400 to 1000°C in air or an atmosphere containing oxygen. Therefore, there is no particular upper limit to the excess amount of carbon, but when expressed as a formula weight ratio, for example, 30
If it becomes too large, the carbon compound that is the raw material will simply be lost, and is preferably 20 or less, more preferably 10 or less. Further comments will be made regarding the effects of the present invention. According to the present invention, compared to methods of physically mixing fine powders of metal oxides and elemental carbon in the gas phase, such as spray drying or conventional methods of combining two carrier gases, Although a homogeneous and finely mixed carbon-containing mixture can be easily obtained, the essential differences are as follows. That is, when comparing the carbon-containing mixture obtained by carrying out the present invention and the mixture particles obtained by spray drying using electron micrographs, it is found that the carbon-containing mixture according to the present invention is composed of one secondary coagulation. It is observed that each particle of carbon and metal oxide is already coexisting in a mixed state and is fine and uniform in the aggregate unit, whereas in the mixture obtained by the spray drying method, each particle is A mixed state in which secondary aggregates (ie, secondary aggregates of carbon particles, secondary aggregates of metal oxide particles) are units is observed. In conventional methods such as spray drying, in which fine powders are physically mixed in the gas phase, no matter how thorough the mixing may seem at first glance, in reality each secondary aggregate is It is nothing more than the smallest unit of mixed content. This is because the particles of the fine powder that are sprayed are already welded to each other and have already formed a grape-shaped secondary aggregate of 50 to 100 particles, and in order to mix the particles uniformly, it is necessary to Next, it is necessary to first break down the aggregates into individual particles, which are their constituent units, by breaking the bonds into pieces, but the bonds in these aggregates are extremely strong, and it is extremely difficult to break them using normal means. be. However, the present invention is not based on the idea of mixing the respective particles that already exist, but instead decomposes the decomposable metal compound and the decomposable carbon compound, which are the raw materials, in hot gas containing water vapor. This method first generates metal oxides and carbon at the molecular level, and simultaneously with the generation, mixing at the molecular level continues, so in principle an extremely uniform and complete mixing state can be obtained. Of course. Therefore, even if nucleation and particle growth occur in the gas phase to produce fine particles, the resulting fine particles subsequently undergo secondary aggregation, but the secondary agglomerates are composed of carbon fine particles and metal oxides. It can be expected that the carbon-containing mixture coexists with fine particles in a mixed state, and such an inference is clearly rejected from the electron micrograph of the carbon-containing mixture of the present invention. In this sense, the present invention is based on a completely new technical idea, and is capable of providing a mixture that is fundamentally and essentially much more uniform and finely mixed than the prior art. In addition,
Regarding the electron micrographs of the above-mentioned carbon-containing mixture, etc., the original application of this application, which is a divisional application, is the patent application filed in 1983.
It is as shown in the attached drawings 2 to 6 of No. 158786. In the present invention, the powder obtained by heat-treating the carbon-containing mixture with excess carbon in the ratio of carbon to metal (formula ratio) is a fine powder in which metal carbide and carbon are in an extremely fine mixed state. This property can be used to create pigments for paints, lacquers, printing inks, etc.; fillers for synthetic resins, rubbers, adhesives, etc.; gas adsorbents, and solid lubricants, refractory aggregates, and steels. It can also be used for purposes such as deoxidizing agents. [Preferred Mode for Carrying Out the Invention] The present invention will be explained in more detail with reference to Examples below. Example 1 Reaction furnace shown in Figure 1 (diameter 300 mm, length 3 m)
Using a duct, air was continuously introduced at 100 Nm ³ /h from the duct 2, and propane gas was supplied at 3 Nm ³ /h from the combustion burner 3 and burned to generate a hot gas flow at 1100 to 1150°C. Next, from nozzle 4, SiCl ₄ was fed at 20 kg/h as a decomposable metal compound, and from nozzle 5, heavy oil A was fed at 25 kg/h as a degradable carbon compound.
After cooling, the dispersoids in the obtained aerosol were collected with a bag filter to obtain the carbon-containing mixture of the present invention. Chemical analysis confirmed that the silicon substance in the mixture was silicon dioxide, and the formula weight ratio of carbon to silicon (g-atom C/g-atom Si, hereinafter the same) was 7.5. Confirmed by gravimetric method. This mixture was heated in argon using a high-frequency heating furnace.
Heated at 1800℃ for 2 hours, cooled down, and heated to 800℃ in air.
℃ to burn off the remaining elemental carbon to obtain about 1.5 kg of finely powdered silicon carbide powder. The specific surface area of this silicon carbide powder was measured to be 9.8.
m ² /g (the specific surface area was measured by the BET method using nitrogen gas adsorption). It was confirmed by powder X-ray diffraction that the crystal shape was cubic. Example 2 The formula weight ratio C/Si was changed in the same manner as in Example 1 except that SiCl ₄ was charged at 10 kg/h and heavy oil A was charged at 15 kg/h.
A carbon-containing mixture of 8.1 was obtained and heated in the same manner to obtain about 2 kg of silicon carbide powder. The specific surface area of the obtained silicon carbide powder was 15.1 m ² /g, and the crystal shape was cubic as in Example 1. Example 3 Ethylene bottoms were used as the hydrocarbon (charging amount 15
A carbon-containing mixture with a formula ratio C/Si = 8.6 was obtained in the same manner as in Example 1, except that Kg/h) was used.
Approximately 1.2 kg of silicon carbide powder was obtained by heating in the same manner. The silicon carbide powder obtained had a specific surface area of 18.6 m ² /g and a cubic crystal shape. Example 4 CH ₃ SiCl ₃ was used as a silicon compound (charge amount 7
A carbon-containing mixture with a formula weight ratio C/Si=14.1 was obtained in exactly the same manner as in Example 3, except that 1 kg/h) was used, and about 1 kg of silicon carbide powder was obtained by heating in the same manner. The specific surface area of the obtained silicon carbide powder was 35.6 m ² /g,
The crystal shape was cubic. Comparative Example 1 SiO ₂ powder (specific surface area: 198.5 m ² /g) and carbon powder (specific surface area: 120.4 m ² /g) were mixed at a formula weight ratio (C/Si) of 10 for 5 hours using a ball mill, and then high-frequency It was heated in a heating furnace at 1800°C in argon for 2 hours, and after cooling, it was heated in air to 800°C to burn off the remaining elemental carbon to obtain about 1 kg of silicon carbide powder (this method is different from conventional technology). ). Although fine powders were used for both SiO ₂ and carbon, the specific surface area of the silicon carbide powder obtained was 1.1 m ² /g.
The crystal shape was cubic. The following Table 1 summarizes the above experimental results.

[Table] As is clear from the following, in the case of the examples using the carbon-containing mixture of the present invention, even though no mechanical pulverization was performed, the results were 10 to 35.
Whereas silicon carbide powder with an extremely wide specific surface area of approximately m ² /g has been obtained, a comparative example using the conventional technology has a specific surface area of 1 digit smaller than this.
Only a specific surface area of about m ² /g has been obtained. In addition, when comparing the transmission electron micrograph images of the silicon carbide powder obtained in Example 1 and the silicon carbide powder obtained in Comparative Example 1, the photos of the silicon carbide powder according to the present invention show that the particles are spherical with a size of 1 μ or less. In contrast, in the silicon carbide powder of Comparative Example 1, coarse particles of 1 μ or more and secondary aggregation were observed in large numbers. Production Example 1 Reactor shown in Figure 1 (used in Example 1)
75Nm ³ /h of air is charged from duct 2, and burner 3 burns propane as the hot air fuel.
TiCl ₄ was charged as a metal compound at a rate of 2Nm ³ /h.
and xylene as a carbon compound were mixed in advance at a weight ratio of 1:2.32 and charged into the furnace through nozzle 5 at 8.01 kg/h. The inside of the furnace is approximately at position A in Figure 1.
It was kept at 1200℃. The aerosol generated in the furnace is extracted from the duct 6, and after cooling, the dispersoid is collected by a back filter to form the carbon-containing mixture of the present invention.
2.52Kg/h (dry weight) was obtained. The mixture contains 59.9 wt% of carbon and 23.9 wt% of titanium (in terms of a single substance) (the remainder is 16.0 wt% of bonding oxygen, 0.1 wt% of carbon-attached hydrogen, and 0.1 wt% or less of others), and the formula weight ratio (C/
Ti) was 10.0, and its specific surface area was 73.2 m ² /g. The Ti in the collected mixture was 99.1% relative to the Ti in the charged TiCl ₄ . (hereinafter referred to as metal collection rate). As a result of ESCA spectrum analysis, only Ti--C bonds were observed as the bond form between Ti and other elements. Production Examples 2 to 11 In addition to propane, methane and hydrogen were also used as the hot air fuel in Production Example 1, and the metal compounds and carbon compounds shown in Table 2 were used to prepare the carbon-containing mixture of the present invention. The results were obtained as shown in Table 2. As a result of the ESCA spectrum analysis, a metal-oxygen bond was observed in all Examples as the bond form between the metal and other elements, and the bond form between the other metal and other elements was Manufacturing Example 2, A slight metal monochlorine bond was observed in 5 and 8. In Table 2, when the metal compound and the carbon compound are charged into the same nozzle, they are mixed and charged in advance. That is, in Production Example 2, WCl ₂ and ethanol were mixed in advance and charged, and in Production Example 3, BCl ₃ was charged separately from nozzle 4, and heavy oil A was charged separately from nozzle 5. Example 5 The carbon-containing mixture of the present invention obtained in Production Example 1 was heated in an argon gas atmosphere at about 2000°C using a high-frequency heating furnace.
The mixture was heated for a period of time, cooled once, and then heated to 700°C in air to burn off the remaining elemental carbon to obtain 5.5 g of finely powdered titanium carbide. The specific surface area of this titanium carbide powder was measured to be 10.2 m ² /g (the specific surface area was measured by the BET method using nitrogen gas adsorption), and the crystal shape of the powder X was cubic.
Confirmed by line diffraction method. The titanium carbide powder was also observed using a transmission electron microscope photograph.

[Table] Comparative example 2 Commercially available industrial TiO ₂ powder (specific surface area 50.5 m ² /g)
and carbon black (specific surface area 65.5 m ² /g) were mixed in water for 2 hours using a wet vibration mill at a weight ratio of 1:1.52 so that the formula weight ratio of carbon to metal was the same as in Production Example 1. and dried using a spray dryer to obtain a mixture of TiO ₂ and carbon black. This mixture was heated using a high-frequency heating furnace in exactly the same manner as in Example 5, and then the elemental carbon was burned off to obtain 5.2 g of cubic titanium carbide powder. The specific surface area of this titanium carbide powder was measured to be 0.7.
m ² /g, which was extremely low. Comparative example 3 TiCl ₃ and carbon black (specific surface area 65.5m ² /
g) was mixed for 2 hours in water using a wet vibration mill at a weight ratio of 1:0.78 to give the same formula weight ratio of carbon to metal as in Example 5, and TiCl in which carbon black was colloidally dispersed was prepared. ₃ aqueous solution was obtained. This was dried using a spray dryer in the same manner as in Comparative Example 2 to obtain a mixture of TiCl ₃ and carbon black. This mixture was heated using a high-frequency heating furnace in exactly the same manner as in Example 5, and then the elemental carbon was burned off to obtain 4.5 g of cubic titanium carbide powder.
When we measured the specific surface area of this titanium carbide powder
It was 1.0 m ² /g, which was extremely low as in Comparative Example 2. This titanium carbide powder was observed using a transmission electron microscope photograph. A comparison between Example 5 and Comparative Examples 2 and 3 shows that when the carbon-containing mixture of the present invention is used, titanium carbide powder with a specific surface area of 10.2 m ² /g is obtained, whereas in the comparative example using the conventional technology However, only a specific surface area that is one order of magnitude smaller than this has been obtained. In addition, in the electron micrograph of the titanium carbide powder of Example 5 of the present invention, only spherical particles with a size of 1 μ or less are observed, whereas in the electron micrograph of the titanium carbide powder of Comparative Example 3, coarse particles of 1 μ or more and It was found that many secondary aggregations were observed. In addition, in Comparative Example 3, by making the metal compound into an aqueous solution state and dispersing carbon black in a colloidal state, the mixed state of the metal and carbon was made more uniform and finer than in Comparative Example 2. However, the specific surface area of the titanium carbide produced by heating the obtained mixture was comparable to that of Comparative Example 2, and the effect of improving the mixing method was hardly seen. I understand. This is presumed to be because even if the metal compound is in a solution state, the mixed state of carbon remains in units of secondary aggregates. Examples 6-15 The mixture obtained in Production Example 1 used in Example 5 was replaced with the mixture obtained in Production Examples 2-11, and each mixture was heated using a high-frequency heating furnace as shown in Table 3. After generating metal carbide under the heating conditions shown in Table 3 in the atmosphere, temperature, and time, the remaining elemental carbon was burned off in air at 700°C, and the heating conditions were as shown in Table 3. A metal carbide powder with the same crystalline shape and specific surface area was obtained. The atmosphere in Examples 11 and 12 is 10 ^-1 ~
This means that it was heated under a reduced pressure of 10 ^-2 mmHg. As a result of observing these metal carbide powders using a transmission electron microscope, it was found that the particle sizes of all the carbides were uniform, and that coarse particles of 1μ or more accounted for less than 10% by weight of each carbide. observed.

【table】 [Brief explanation of the drawing]

FIG. 1 is a sectional view showing one example of a reactor used in carrying out the present invention. In the drawings 1... Furnace material, 2... Duct, 3... Combustion burner, 4
...Nozzle, 5...Nozzle, 6...Duct.

Claims (1)

[Claims] 1. A decomposable metal compound and a decomposable carbon compound are charged and decomposed into a hot gas containing water vapor to obtain a mixed aerosol dispersoid containing aerosols of metal oxides and elemental carbon, and this decomposed product is A method for producing a metal carbide, which comprises heating a carbon-containing mixture obtained by collection.